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Pearl oysters have been extensively utilized in pearl production; however, most pearl oyster shells are discarded as industrial waste. In a previous study, we demonstrated that the intraperitoneal administration of pearl oyster shell-derived nacre extract (NE) prevented d-galactose-induced brain and skin aging. In this study, we examined the anti-aging effects of orally administered NE in senescence-accelerated mice (SAMP8). Feeding SAMP8 mice NE prevented the development of aging-related characteristics, such as coarse and dull hair, which are commonly observed in aged mice. Additionally, the NE mitigated muscle aging in SAMP8 mice, such as a decline in grip strength. Histological analysis of skeletal muscle revealed that the NE suppressed the expression of aging markers, cyclin-dependent kinase inhibitor 2A (p16) and cyclin-dependent kinase inhibitor 1 (p21), and increased the expression of sirtuin1 and peroxisome proliferator-activated receptor gamma coactivator 1 (PGC1)- α, which are involved in muscle synthesis. These findings suggest that the oral administration of NE suppresses skeletal muscle aging. Moreover, NE administration suppressed skin aging, including a decline in water content. Interestingly, oral administration of NE significantly extended the lifespan of SAMP8 mice, suggesting that its effectiveness as an anti-aging agent of various tissues including skeletal muscle, skin, and adipose tissue.
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Muscle aging contributed to morbidity and mortality in the elderly adults by leading to severe outcomes such as frailty, falls and fractures. Post-transcriptional regulation especially competing endogenous RNA (ceRNA) mechanism may modulate the process of skeletal muscle aging. RNA-seq was performed in quadriceps of 6-month-old (adult) and 22-month-old (aged) male mice to identify differentially expressed ncRNAs and mRNAs and further construct ceRNA networks. Decreased quadriceps-body weight ratio and muscle fiber cross-sectional area as well as histological characteristics of aging were observed in the aged mice. Besides, there were higher expressions of atrogin-1 and MuRF-1 and lower expression of Myog, Myf4 and Myod1 in the quadriceps of aged mice relative to that of adult mice. The expression of 85 lncRNAs, 52 circRNAs, 10 miRNAs and 277 mRNAs were significantly dysregulated in quadriceps between the two groups, among which two ceRNA networks lncRNA 2700081O15Rik/circRNA_0000820-miR-673-3p-Tmem120b were constructed. Level of triglycerides and expression of PPARγ, C/EBPα, FASN and leptin were elevated and the expression of adiponectin was reduced in quadriceps of aged mice compared with that of adult mice. LncRNA 2700081O15Rik/circRNA_0000820-miR-673-3p-Tmem120b were possibly associated with the adipogenesis and fat accumulation in skeletal muscle of age male mice.
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Envejecimiento , Animales , Masculino , Ratones , Envejecimiento/metabolismo , Músculo Esquelético/metabolismo , Redes Reguladoras de Genes , MicroARNs/metabolismo , MicroARNs/genética , ARN Largo no Codificante/metabolismo , ARN Largo no Codificante/genética , ARN Mensajero/metabolismo , ARN Mensajero/genética , ARN Circular/metabolismo , ARN Circular/genética , Músculo Cuádriceps/metabolismo , ARN Endógeno CompetitivoRESUMEN
BACKGROUND: The study aimed to investigate the effect of Glucagon-like peptide-2 (GLP-2) on muscle aging in vivo and in vitro. METHODS: Six-week-old C57BL/6J mice were administered with D-galactose (200 mg/kg/day, intraperitoneally) for 8weeks, followed by daily subcutaneous injections of GLP-2 (300 or 600 µg/kg/day) for 4weeks. Skeletal muscle function and mass were evaluated using relative grip strength and muscle weight. The sizes and types of muscle fibers and apoptosis were assessed through histological analysis, immunofluorescence staining, and TUNEL staining, respectively. C2C12 myotubes were treated with D-galactose (40 mg/mL) and GLP-2. Protein expression of differentiation-related myogenic differentiation factor D (MyoD), myogenin (MyoG), and myosin heavy chain (Myhc), degradation-related Muscle RING finger 1 (MuRF-1), and muscle atrophy F-box (MAFbx)/Atrogin-1, and apoptosis-related B-cell leukemia/lymphoma 2 (Bcl-2) and Bax, were assessed using western blots. The Pi3k inhibitor LY294002 was applied to investigate whether GLP-2 regulated myogenesis and myotube aging via IGF-1/Pi3k/Akt/FoxO3a signaling pathway. RESULTS: The results demonstrated that GLP-2 significantly reversed the decline in muscles weight, relative grip strength, diameter, and cross-sectional area of muscle fibers induced by D-galactose in mice. Apart from suppressing the expressions of MuRF-1 and Atrogin-1 in the muscles and C2C12 myotubes, GLP-2 significantly increased the expressions of MyoD, MyoG, and Myhc compared to the D-galactose. GLP-2 significantly suppressed cell apoptosis. Western blot analysis indicated that the regulation of GLP-2 may be attributed to the activation of theIGF-1/Pi3k/Akt/FoxO3a phosphorylation pathway. CONCLUSIONS: This study suggested that GLP-2 ameliorated D-galactose induced muscle aging by IGF-1/Pi3k/Akt/FoxO3a pathway.
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Proteína Forkhead Box O3 , Galactosa , Péptido 2 Similar al Glucagón , Factor I del Crecimiento Similar a la Insulina , Ratones Endogámicos C57BL , Músculo Esquelético , Fosfatidilinositol 3-Quinasas , Proteínas Proto-Oncogénicas c-akt , Transducción de Señal , Animales , Ratones , Proteína Forkhead Box O3/metabolismo , Transducción de Señal/efectos de los fármacos , Factor I del Crecimiento Similar a la Insulina/metabolismo , Factor I del Crecimiento Similar a la Insulina/farmacología , Proteínas Proto-Oncogénicas c-akt/metabolismo , Péptido 2 Similar al Glucagón/farmacología , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Fosfatidilinositol 3-Quinasas/metabolismo , Envejecimiento/efectos de los fármacos , Apoptosis/efectos de los fármacos , Masculino , Fibras Musculares Esqueléticas/efectos de los fármacos , Fibras Musculares Esqueléticas/metabolismo , Fibras Musculares Esqueléticas/patologíaRESUMEN
AIM: Sarcopenia, the aging-related loss of muscle mass and function, is a debilitating process negatively impacting the quality of life of affected individuals. Although the mechanisms underlying sarcopenia are incompletely understood, impairments in mitochondrial dynamics, including mitochondrial fusion, have been proposed as a contributing factor. However, the potential of upregulating mitochondrial fusion proteins to alleviate the effects of aging on skeletal muscles remains unexplored. We therefore hypothesized that overexpressing Mitofusin 2 (MFN2) in skeletal muscle in vivo would mitigate the effects of aging on muscle mass and improve mitochondrial function. METHODS: MFN2 was overexpressed in young (7 mo) and old (24 mo) male mice for 4 months through intramuscular injections of an adeno-associated viruses. The impacts of MFN2 overexpression on muscle mass and fiber size (histology), mitochondrial respiration, and H2O2 emission (Oroboros fluororespirometry), and various signaling pathways (qPCR and western blotting) were investigated. RESULTS: MFN2 overexpression increased muscle mass and fiber size in both young and old mice. No sign of fibrosis, necrosis, or inflammation was found upon MFN2 overexpression, indicating that the hypertrophy triggered by MFN2 overexpression was not pathological. MFN2 overexpression even reduced the proportion of fibers with central nuclei in old muscles. Importantly, MFN2 overexpression had no impact on muscle mitochondrial respiration and H2O2 emission in both young and old mice. MFN2 overexpression attenuated the increase in markers of impaired autophagy in old muscles. CONCLUSION: MFN2 overexpression may be a viable approach to mitigate aging-related muscle atrophy and may have applications for other muscle disorders.
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Advanced glycation end-products (AGEs) stochastically accrue in skeletal muscle and on collagen over an individual's lifespan, stiffening the muscle and modifying the stem cell (MuSC) microenvironment while promoting proinflammatory, antiregenerative signaling via the receptor for advanced glycation end-products (RAGEs). In the present study, a novel in vitro model was developed of this phenomenon by cross linking a 3-D collagen scaffold with AGEs and investigating how myoblasts responded to such an environment. Briefly, collagen scaffolds were incubated with d-ribose (0, 25, 40, 100, or 250 mM) for 5 days at 37°C. C2C12 immortalized mouse myoblasts were grown on the scaffolds for 6 days in growth conditions for proliferation, and 12 days for differentiation and fusion. Human primary myoblasts were also used to confirm the C2C12 data. AGEs aberrantly extended the DNA production stage of C2C12s (but not in human primary myoblasts) which is known to delay differentiation in myogenesis, and this effect was prevented by RAGE inhibition. Furthermore, the differentiation and fusion of myoblasts were disrupted by AGEs, which were associated with reductions in integrins and suppression of RAGE. The addition of S100b (RAGE agonist) recovered the differentiation and fusion of myoblasts, and the addition of RAGE inhibitors (FPS-ZM1 and Azeliragon) inhibited the differentiation and fusion of myoblasts. Our results provide novel insights into the role of the AGE-RAGE axis in skeletal muscle aging, and future work is warranted on the potential application of S100b as a proregenerative factor in aged skeletal muscle.NEW & NOTEWORTHY Collagen cross-linked by advanced glycation end-products (AGEs) induced myoblast proliferation but prevented differentiation, myotube formation, and RAGE upregulation. RAGE inhibition occluded AGE-induced myoblast proliferation, while the delivery of S100b, a RAGE ligand, recovered fusion deficits.
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Reacción de Maillard , Músculo Esquelético , Ratones , Humanos , Animales , Anciano , Receptor para Productos Finales de Glicación Avanzada/metabolismo , Músculo Esquelético/metabolismo , Mioblastos/metabolismo , Diferenciación Celular/fisiología , Colágeno , Desarrollo de Músculos , Productos Finales de Glicación Avanzada , Subunidad beta de la Proteína de Unión al Calcio S100RESUMEN
BACKGROUND:Sarcopenia is a progressive,generalized skeletal muscle disease that is closely related to the occurrence of osteoarthritis,fractures,limb disability and death in the elderly.Establishing animal models of sarcopenia is essential to understand the pathophysiology of sarcopenia and to identify effective treatment strategies. OBJECTIVE:To review the evaluation criteria of mouse models of sarcopenia and the modeling methods of mouse models of sarcopenia,and to analyze and compare the advantages and disadvantages of various modeling methods,in order to provide reference for the research and diagnosis and treatment of sarcopenia. METHODS:"Sarcopenia,skeletal muscle aging,mouse model,animal model"in Chinese and English were used as Chinese and English search terms,respectively.The search formula was"(sarcopenia OR skeletal muscle aging)AND(mouse model OR animal model)."CNKI,WanFang and PubMed were searched for related articles published from January 2010 and October 2022.A total of 59 articles were finally included for analysis. RESULTS AND CONCLUSION:There is a faster modeling time in SAMP8 mice and the type of muscle atrophy is consistent with that of patients with sarcopenia.Therefore,it is an ideal model.Although the surgical method can successfully induce muscle atrophy,it requires precise surgical operation,which is difficult and time-consuming.Hindlimb suspension modeling in mice is similar to that of the elderly and can be regarded as an effective model of senile sarcopenia.Although reagent injection molding is simple to perform,both the dose and number of days of administration of reagents are not clear and need to be further investigated.Transgenic mouse models are less commonly used and their model stability needs further study.The search for a mouse model with low cost,short time consumption and high simulation of human sarcopenia is still a future research direction.
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BACKGROUND:Exercise as a viable non-pharmacological treatment has the potential to reverse skeletal muscle aging that deteriorates with age.The role of autophagy in the skeletal muscle aging process is indispensable.During skeletal muscle aging,Atg genes involved in regulating autophagy regulate the autophagic process in either a facilitative or inhibitory manner to improve the physiological morphology of skeletal muscle.However the specific molecular mechanisms of autophagy in the exercise regulation of skeletal muscle aging remain puzzling. OBJECTIVE:To search for general patterns of the effects of autophagic mechanisms on skeletal muscle aging during exercise through a review of articles in this field. METHODS:(1)CNKI and Web of Science were searched,reviewed,and screened for relevant literature using the keywords of"Atg genes(proteins),autophagy,exercise,and skeletal muscle aging"to lay the theoretical foundation for the full-text analysis.(2)The comparative analysis method was used to compare the similarities and differences among the included documents to provide reasonable theoretical support for the arguments.By the further comparative analysis of the literature,the relationship between relevant indicators was clarified,to provide the ideas for the full-text analysis. RESULTS AND CONCLUSION:Atg family-mediated autophagy is indispensable for delaying skeletal muscle aging.Atg genes involved in regulating autophagy regulate the autophagic process in either a facilitative or inhibitory manner to improve the physiological morphology and function of skeletal muscle.Different exercise patterns,such as age,time,or intensity at initiation,may have heterogeneous effects on the expression of autophagy-related proteins,but long-term aerobic exercise regulates Atg-related proteins,induces skeletal muscle autophagy,and delays the loss of muscle mass.
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Sarcopenia induced by muscle aging is associated with negative outcomes in a variety of diseases. Long non-coding RNAs are a class of RNAs longer than 200 nucleotides with lower protein coding potential. An increasing number of studies have shown that lncRNAs play a vital role in skeletal muscle development. According to our previous research, lncRNA GPRC5D-AS1 is selected in the present study as the target gene to further study its effect on skeletal muscle aging in a dexamethasone-induced human muscle atrophy cell model. As a result, GPRC5D-AS1 functions as a ceRNA of miR-520d-5p to repress cell apoptosis and regulate the expression of muscle regulatory factors, including MyoD, MyoG, Mef2c and Myf5, thus accelerating myoblast proliferation and differentiation, facilitating development of skeletal muscle. In conclusion, lncRNA GPRC5D-AS1 could be a novel therapeutic target for treating sarcopenia.
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MicroARNs , ARN Largo no Codificante , Sarcopenia , Humanos , MicroARNs/genética , MicroARNs/metabolismo , ARN Largo no Codificante/genética , ARN Largo no Codificante/metabolismo , ARN Endógeno Competitivo , Sarcopenia/genética , Proliferación Celular/genética , Envejecimiento/genética , Músculo Esquelético/metabolismo , Regulación Neoplásica de la Expresión Génica , Línea Celular Tumoral , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismoRESUMEN
BACKGROUND: The aging of skeletal muscle is the leading cause of physical disability in older adults, currently effective treatment methods are lacking. Ginsenoside Rh4, an active component extracted from ginseng, possesses beneficial anti-inflammatory and anti-oxidative effects. PURPOSE: The aim of this study was to elucidate the antioxidant effect of ginsenoside Rh4 on aging skeletal muscle and its molecular mechanism of anti-aging of skeletal muscle. STUDY DESIGN: In this study, we employed a D-galactose-induced model of skeletal muscle aging to investigate whether ginsenoside Rh4 can delay the process of skeletal muscle senescence. METHODS: The effects of ginsenoside Rh4 on oxidative damage and inflammation in aging skeletal muscle were analyzed using immunofluorescence, immunohistochemistry, ELISA kits, H&E staining, flow cytometry, and protein immunoblotting. The changes of ginsenoside Rh4 on mitochondrial morphology were observed by transmission electron microscopy, and ELISA kits and protein immunoblotting analyzed the effects of ginsenoside Rh4 on mitochondrial homeostasis in skeletal muscle cells. The influence of ginsenoside Rh4 on the SIRT1 signaling pathway in aging skeletal muscle were investigated by protein immunoblotting, immunofluorescence, and ß-galactosidase staining. RESULTS: Our results showed that Rh4 improved the morphology of muscle fibers and produced an anti-inflammatory response. Furthermore, in vitro experiments indicated that ginsenosides reduced the production of senescent cells, while Rh4 effectively alleviated oxidative damage in skeletal muscle and restored mitochondrial balance. Transcriptome analysis and molecular docking showed that Rh4 improved mitochondrial homeostasis and delayed skeletal muscle aging by regulating the PGC-1α-TFAM and HIF-1α-c-Myc pathways via targeting SIRT1. CONCLUSION: Ginsenoside Rh4 improves oxidative stress and inflammation in skeletal muscle by activating SIRT1, deacetylating Nrf2, regulating PGC-1α-TFAM and HIF-1α-c-Myc pathways, and enhancing mitochondrial homeostasis, thus achieving the effect of delaying skeletal muscle aging.
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Ginsenósidos , Ginsenósidos/farmacología , Sirtuina 1 , Simulación del Acoplamiento Molecular , Músculo EsqueléticoRESUMEN
A mechanistic understanding of cell-autonomous skeletal muscle changes after injury can lead to novel interventions to improve functional recovery in an aged population. However, major knowledge gaps persist owing to limitations of traditional biological aging models. 2D cell culture represents an artificial environment, while aging mammalian models are contaminated by influences from non-muscle cells and other organs. Here, a 3D muscle aging system is created to overcome the limitations of these traditional platforms. It is shown that old muscle constructs (OMC) manifest a sarcopenic phenotype, as evidenced by hypotrophic myotubes, reduced contractile function, and decreased regenerative capacity compared to young muscle constructs. OMC also phenocopy the regenerative responses of aged muscle to two interventions, pharmacological and biological. Interrogation of muscle cell-specific mechanisms that contribute to impaired regeneration over time further reveals that an aging-induced increase of complement component 4b (C4b) delays muscle progenitor cell amplification and impairs functional recovery. However, administration of complement factor I, a C4b inactivator, improves muscle regeneration in vitro and in vivo, indicating that C4b inhibition may be a novel approach to enhance aged muscle repair. Collectively, the model herein exhibits capabilities to study cell-autonomous changes in skeletal muscle during aging, regeneration, and intervention.
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Complemento C4b , Músculo Esquelético , Animales , Envejecimiento/fisiología , Fibras Musculares Esqueléticas , Contracción Muscular , MamíferosRESUMEN
Introduction: Avian eggshell membrane (ESM) is a complex extracellular matrix comprising collagens, glycoproteins, proteoglycans, and hyaluronic acid. We have previously demonstrated that ESM possesses anti-inflammatory properties in vitro and regulates wound healing processes in vivo. The present study aimed to investigate if oral intake of micronized ESM could attenuate skeletal muscle aging associated with beneficial alterations in gut microbiota profile and reduced inflammation. Methods: Elderly male C57BL/6 mice were fed an AIN93G diet supplemented with 0, 0.1, 1, or 8% ESM. Young mice were used as reference. The digestibility of ESM was investigated using the static in vitro digestion model INFOGEST for older people and adults, and the gut microbiota profile was analyzed in mice. In addition, we performed a small-scale pre-clinical human study with healthy home-dwelling elderly (>70 years) who received capsules with a placebo or 500 mg ESM every day for 4 weeks and studied the effect on circulating inflammatory markers. Results and discussion: Intake of ESM in elderly mice impacted and attenuated several well-known hallmarks of aging, such as a reduction in the number of skeletal muscle fibers, the appearance of centronucleated fibers, a decrease in type IIa/IIx fiber type proportion, reduced gene expression of satellite cell markers Sdc3 and Pax7 and increased gene expression of the muscle atrophy marker Fbxo32. Similarly, a transition toward the phenotypic characteristics of young mice was observed for several proteins involved in cellular processes and metabolism. The digestibility of ESM was poor, especially for the elderly condition. Furthermore, our experiments showed that mice fed with 8% ESM had increased gut microbiota diversity and altered microbiota composition compared with the other groups. ESM in the diet also lowered the expression of the inflammation marker TNFA in mice and in vitro in THP-1 macrophages. In the human study, intake of ESM capsules significantly reduced the inflammatory marker CRP. Altogether, our results suggest that ESM, a natural extracellular biomaterial, may be attractive as a nutraceutical candidate with a possible effect on skeletal muscle aging possibly through its immunomodulating effect or gut microbiota.
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Angiogenesis is the physiological process of capillary growth. It is strictly regulated by the balanced activity of agents that promote the formation of capillaries (pro-angiogenic factors) on the one hand and inhibit their growth on the other hand (anti-angiogenic factors). Capillary rarefaction and insufficient angiogenesis are some of the main causes that limit blood flow during aging, whereas physical training is a potent non-pharmacological method to intensify capillary growth in the musculoskeletal system. The main purpose of this study is to present the current state of knowledge concerning the key signalling molecules implicated in the regulation of skeletal muscle and bone angiogenesis during aging and physical training.
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Ejercicio Físico , Músculo Esquelético , Músculo Esquelético/irrigación sanguínea , Neovascularización Fisiológica/fisiología , Fenómenos Fisiológicos CardiovascularesRESUMEN
Whey protein has been reported to be an impactful dietary supplement to ameliorate skeletal muscle aging for a long time. However, whether whey protein could contribute to muscle aging amelioration by post-transcriptional modulation remains unclear. In this study, 19-month-old mice orally received whey protein supplementation (1.0 g/kg/bw/d, whey protein group) or deionized water (the control group) for 3 months. Differentially expressed ncRNAs and mRNAs in quadriceps were identified by RNA-seq. Construction of non-coding RNAs (ncRNAs)-associated competing endogenous RNA (ceRNA) networks as well as GO and KEGG enrichment analyses were also carried out subsequently. Meanwhile, ultrasound measurement, H&E staining, myofiber cross-sectional area measurement, western blotting and RT-qPCR were performed in the quadriceps to evaluate muscle status and verify the RNA-seq data. Whey protein supplementation for 3 months increased quadriceps-body weight ratio and improved the histological as well as ultrasonographic characteristics of aging in muscle. Moreover, the protein expression levels of Myog, Myf4, Myf5 and MyoD1 were all significantly elevated in quadriceps. The expression of 90 lncRNAs, 334 mRNAs, six circRNAs and 52 miRNAs were significantly up or down-regulated in quadriceps after whey protein supplementation. Furthermore, ncRNAs-associated networks and GO and KEGG enrichment analyses revealed whey protein may influence muscle aging process through selected ncRNAs-associated ceRNA networks. Therefore, post-transcriptional modulation could be a potential crucial way to ameliorate skeletal muscle aging after whey protein supplementation. The selected ncRNAs-associated ceRNA networks may provide new insight for the underlying mechanism and profound therapeutic target for skeletal muscle aging.
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MicroARNs , ARN Largo no Codificante , Envejecimiento/genética , Animales , Suplementos Dietéticos , Redes Reguladoras de Genes , Ratones , MicroARNs/genética , Músculo Esquelético/metabolismo , ARN Largo no Codificante/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Proteína de Suero de Leche/farmacologíaRESUMEN
Advanced age causes skeletal muscle to undergo deleterious changes including muscle atrophy, fast-to-slow muscle fiber transition, and an increase in collagenous material that culminates in the age-dependent muscle wasting disease known as sarcopenia. Advanced glycation end-products (AGEs) non-enzymatically accumulate on the muscular collagens in old age via the Maillard reaction, potentiating the accumulation of intramuscular collagen and stiffening the microenvironment through collagen cross-linking. This review contextualizes known aspects of skeletal muscle extracellular matrix (ECM) aging, especially the role of collagens and AGE cross-linking, and underpins the motor nerve's role in this aging process. Specific directions for future research are also discussed, with the understudied role of AGEs in skeletal muscle aging highlighted. Despite more than a half century of research, the role that intramuscular collagen aggregation and cross-linking plays in sarcopenia is well accepted yet not well integrated with current knowledge of AGE's effects on muscle physiology. Furthermore, the possible impact that motor nerve aging has on intramuscular cross-linking and muscular AGE levels is posited.
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BACKGROUND AND OBJECTIVE: Sympathetic activity plays an important role in the proliferation and differentiation of stem cells, and it changes over time, thereby exerting differential effects on various stem cell types. Aging causes sympathetic hyperactivity in aged tissues and blunts sympathetic nerves regulation, and sympathetic abnormalities play a role in aging-related diseases. Currently, the effect of sympathetic activity on skeletal muscle stem cells, namely satellite cells (SCs), is unclear. This study aimed to investigate the effects of skeletal muscle sympathetic activity on SC aging and skeletal muscle repair. MATERIALS AND METHODS: To evaluate skeletal muscle and fibrotic areas, numbers of SCs and myonuclei per muscle fiber, ß2-adrenoceptor (ß2-ADR) expression, muscle repair, and sympathetic innervation in skeletal muscle, aged mice, young mice that underwent chemical sympathectomy (CS) were utilized. Mice with a tibialis anterior muscle injury were treated by barium chloride (BaCl2) and clenbuterol (CLB) in vivo. SCs or C2C12 cells were differentiated into myotubes and treated with or without CLB. Immunofluorescence, western blot, sirius red, and hematoxylin-eosin were used to evaluate SCs, myogenic repair and differentiation. RESULTS: The number of SCs, sympathetic activity, and reparability of muscle injury in aged mice were significantly decreased, compared with those in young mice. The above characteristics of young mice that underwent CS were similar to those of aged mice. While CLB promoted the repair of muscle injury in aged and CS mice and ameliorated the reduction in the SC number and sympathetic activity, the effects of CLB on the SCs and sympathetic nerves in young mice were not significant. CLB inhibited the myogenic differentiation of C2C12 cells in vitro. We further found that NF-κB and ERK1/2 signaling pathways were activated during myogenic differentiation, and this process could be inhibited by CLB. CONCLUSION: Normal sympathetic activity promoted the stemness of SCs to thereby maintain a steady state. It also could maintain total and self-renewing number of SCs and maintain a quiescent state, which was correlated with skeletal SCs via ß2-ADR. Normal sympathetic activity was also beneficial for the myogenic repair of injured skeletal muscle.
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Células Satélite del Músculo Esquelético , Envejecimiento , Animales , Diferenciación Celular , Proliferación Celular , Senescencia Celular , Ratones , Desarrollo de Músculos , Músculo Esquelético , Receptores AdrenérgicosRESUMEN
Decellularized tissues are biocompatible materials that engraft well, but the age of their source has not been explored for clinical translation. Advanced glycation end products (AGEs) are chemical cross-links that accrue on skeletal muscle collagen in old age, stiffening the matrix and increasing inflammation. Whether decellularized biomaterials derived from aged muscle would suffer from increased AGE collagen cross-links is unknown. We characterized gastrocnemii of 1-, 2-, and 20-month-old C57BL/6J mice before and after decellularization to determine age-dependent changes to collagen stiffness and AGE cross-linking. Total and soluble collagen was measured to assess if age-dependent increases in collagen and cross-linking persisted in decellularized muscle matrix (DMM). Stiffness of aged DMM was determined using atomic force microscopy. AGE levels and the effect of an AGE cross-link breaker, ALT-711, were tested in DMM samples. Our results show that age-dependent increases in collagen amount, cross-linking, and general stiffness were observed in DMM. Notably, we measured increased AGE-specific cross-links within old muscle, and observed that old DMM retained AGE cross-links using ALT-711 to reduce AGE levels. In conclusion, deleterious age-dependent modifications to collagen are present in DMM from old muscle, implying that age matters when sourcing skeletal muscle extracellular matrix as a biomaterial.
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Envejecimiento/metabolismo , Colágeno/metabolismo , Matriz Extracelular/metabolismo , Productos Finales de Glicación Avanzada/metabolismo , Músculo Esquelético/metabolismo , Envejecimiento/patología , Animales , Matriz Extracelular/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Músculo Esquelético/patologíaRESUMEN
Age-related skeletal muscle deterioration (sarcopenia) has a significant effect on the elderly's health and quality of life, but the molecular and gene regulatory mechanisms remain largely unknown. It is necessary to identify the candidate genes related to skeletal muscle aging and prospective therapeutic targets for effective treatments. The age-line-related genes (ALRGs) and age-line-related transcripts (ALRTs) were investigated using the gene expression profiles of GSE47881 and GSE118825 from the Gene Expression Omnibus (GEO) database. The protein-protein interaction (PPI) networks were performed to identify the key molecules with Cytoscape, and Gene Set Enrichment Analysis (GSEA) was used to clarify the potential molecular functions. Two hub molecules were finally obtained and verified with quantitative real-time PCR (qRT-PCR). The results showed that the expression of mitochondria genes involved in mitochondrial electron transport, complex assembly of the respiratory chain, tricarboxylic acid cycle, oxidative phosphorylation, and ATP synthesis were down-regulated in skeletal muscle with aging. We further identified a primary hub gene of CYCS (Cytochrome C) and a key transcription factor of ESRRA (Estrogen-related Receptor Alpha) to be associated closely with skeletal muscle aging. PCR analysis confirmed the expressions of CYCS and ESRRA in gastrocnemius muscles of mice of different ages were significantly different, and decreased gradually with age. In conclusion, the main cause of skeletal muscle aging may be the systematically reduced expression of mitochondrial functional genes. The CYCS and ESRRA may play significant roles in the progression of skeletal muscle aging and serve as potential biomarkers for future diagnosis and treatment.
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Envejecimiento/genética , Citocromos c/genética , Mitocondrias/genética , Músculo Esquelético/metabolismo , Receptores de Estrógenos/genética , Adolescente , Adulto , Anciano , Envejecimiento/metabolismo , Niño , Citocromos c/metabolismo , Humanos , Persona de Mediana Edad , Mapas de Interacción de Proteínas/genética , Receptores de Estrógenos/metabolismo , Transcriptoma/genética , Adulto Joven , Receptor Relacionado con Estrógeno ERRalfaRESUMEN
OBJECTIVE: Sleep breathing disorder may affect skeletal muscle decline in the elderly, but the mechanism is not clear. Therefore, this study explores the mechanism of skeletal muscle aging in chronic intermittent hypoxia (CIH) rats. METHODS: In vitro and in vivo CIH models were constructed in L6 cells and SD rats by treating chronic intermittent hypoxia. Pathological changes of skeletal muscle in vivo were measured by hematoxylin-eosin (HE) staining. Cell proliferation and apoptosis were detected by CCK-8 and Flow cytometer, respectively. The expression of KLC1/GRX1 and the proteins related to the Wnt/ß-catenin pathway were measured by qRT-PCR and western blot. RESULTS: CIH model was successfully established induced by chronic intermittent hypoxia with lower skeletal muscle index (SMI), increased inward migration of muscle fiber cell nucleus, and muscle cells' distance. The results showed that Wnt/ß-catenin signalling was activatedin both L6 cells and CIH rats' model. KLC1 and GRX1 were significantly downregulated in the CIH model. Loss of function showed that downregulation of KLC1 promoted L6 cell and skeletal muscle aging in vitro and in vivo, respectively. CONCLUSION: Our results demonstrated that CIH aggravated skeletal muscle aging by down-regulating KLC1/GRX1 expression via the Wnt/ß-catenin pathway.
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Cateninas , Hipoxia , Anciano , Envejecimiento , Animales , Humanos , Cinesinas , Proteínas Asociadas a Microtúbulos , Músculo Esquelético , Ratas , Ratas Sprague-DawleyRESUMEN
GRSF1 is a mitochondrial RNA-binding protein important for maintaining mitochondrial function. We found that GRSF1 is highly expressed in cultured skeletal myoblasts differentiating into myotubes. To understand the physiological function of GRSF1 in vivo, we generated mice in which GRSF1 was specifically ablated in skeletal muscle. The conditional knockout mice (Grsf1cKO) appeared normal until 7-9 months of age. Importantly, however, a reduction of muscle endurance compared to wild-type controls was observed in 16- to 18-month old Grsf1cKO mice. Transcriptomic analysis revealed more than 200 mRNAs differentially expressed in Grsf1cKO muscle at this age. Notably, mRNAs encoding proteins involved in mitochondrial function, inflammation, and ion transport, including Mgarp, Cxcl10, Nfkb2, and Sln mRNAs, were significantly elevated in aged Grsf1cKO muscle. Our findings suggest that GRSF1 deficiency exacerbates the functional decline of aged skeletal muscle, likely through multiple downstream effector proteins.
Asunto(s)
Envejecimiento/metabolismo , Músculo Esquelético/metabolismo , Resistencia Física , Proteínas de Unión a Poli(A)/deficiencia , Animales , Diferenciación Celular/genética , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Ratones Endogámicos C57BL , Ratones Noqueados , Células Musculares/metabolismo , Desarrollo de Músculos/genética , Proteínas de Unión a Poli(A)/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Especies Reactivas de Oxígeno/metabolismoRESUMEN
This study aimed to identify long non-coding RNAs (lncRNAs) involving in the skeletal muscle aging process. Skeletal muscle samples from old and young subjects were collected for lncRNA-sequencing. Differentially expressed genes (DEGs) and DElncRNAs between young and old groups were identified and a co-expression network was built. Further, a dexamethasone-induced muscle atrophy cell model was established to characterize the function of a critical lncRNA. A total of 424 DEGs, including 271 upregulated genes and 153 downregulated genes as well as 152 DElncRNAs including 76 up-regulated and 76 down-regulated lncRNAs were obtained. Functional analysis demonstrated that the DEGs were significantly related to immune response. Coexpression network demonstrated lncRNA AC004797.1, PRKG1-AS1 and GRPC5D-AS1 were crucial lncRNAs. Their expressions were further validated by qRT-PCR in human skeletal muscle and the muscle atrophy cell model. Further in vitro analysis suggested that knock-down of PRKG1-AS1 could significantly increase cell viability and decrease cell apoptosis. qRT-PCR and western blot analyses demonstrated that knock-down of PRKG1-AS1 could increase the expression of MyoD, MyoG and Mef2c. This study demonstrated that lncRNAs of GPRC5D-AS1, AC004797.1 and PRKG1-AS1 might involve the aging-associated disease processes.